Evaluation of Yellow-poplar Decline in Indiana
Stephen G. Krecik and Philip T. Marshall
Introduction
Indiana Department of Natural Resources, Division of Forestry, P.O. Box 218, Vallonia, IN 47281
Results
Yellow-poplar (Liriodendron tulipfera) is an important component of Indiana’s
hardwood forests. The species comprises nearly 13% of state sawtimber volume,
and the stand is valued at well over $800 million using current stumpage prices.
Yellow-poplar grows best on rich, mesic sites and has been long regarded a
drought-sensitive forest species.
Indiana foresters have reported pockets of declining yellow-poplar in
southeastern parts of the state, following substantial, prolonged droughts in 1999
and 2002. Decline symptoms include chlorosis of leaves, sparse crown, dieback,
trunk and branch cankers, and root sprouts, and epicormic sprouting.
Extent of Decline: Approximately 10% of yellow-poplar trees encountered were in poor
condition, 58% in fair condition, and 32% in good condition.
Yellow-poplar decline associated with site parameters: Decline symptoms were
significantly correlated with aspect, diameter, crown position, crown light, and crown density
(Fig. 1-5). Mortality (measured by standing snags) accounted for a 5.2% loss of yellow-poplar
trees, and was significantly correlated with smaller diameter classes (results not pictured).
Yellow-poplar Decline
Symptoms
1. Bark splits.
2. Trunk and branch cankers.
3. Leaf chlorosis.
4. Branch dieback.
5. Witches’ brooms.
6. Root collar and epicormic sprouts.
In this study, observations were conducted on 223 yellow-poplar trees in 62
prism plots at 12 locations. The purpose of this study was to identify factors
associated with yellow-poplar decline in southeastern Indiana and evaluate the
effectiveness of FHM/FIA data and methods in detecting yellow-poplar decline.
7. Shortened internodes on lateral
branches.
Deliquescent branching, showing loss of
apical dominance on slow-growing lateral
branches.
Southeastern Indiana
showing yellow-poplar
decline study locations
Steve Krecik - IDNR
8. Tree mortality.
Figure 1: Relationship of Aspect and Tree Condition
Chi-Square = 34.17051, df = 4, p = .0001
Fusarium solani cankers
on yellow poplar
Root collar sprouts
USDA Forest Service
Steve Krecik - IDNR
Figure 2: Relationship of Tree Diameter and Tree Condition
Chi-Square = 17.16663, df = 9, p = .0462
Prism plot locations at Berger
Woods in Harrison County
Phil Marshal - IDNR
Figure 3: Relationship of Crown Position and Tree Condition
Chi-Square = 8.099007, df = 3, p = .0440
Methods
Figure 4: Relationship of Crown Light and Tree Condition
Chi-Square = 15.64156, df = 5, p = .0080
Note on Tree Condition Rating: Trees rated on
decline symptoms (see box at left) as either:
Good: 1-2 (vigorous, little or no observable
decline);
Foresters working in southeast Indiana were surveyed during spring 2004, to
locate tracts of declining yellow-poplar. A reconnaissance survey was conducted
in each tract
Fair: 3-5 (moderate decline symptoms); and
Poor: 6-8 (heavy decline symptoms and poor
vigor).
Tracts with sufficiently extensive areas and numbers of decline-symptom trees
were surveyed using 10 basal area factor prism plots. Parameters measured in
each plot include:
1. Plot Data (62 plots):
•topographical position;
Yellow-poplar decline and incremental growth: Yellow-poplar averaged 3.5 mm of
incremental (radial) growth per year (1995-2004).
Drought affected radial growth:
Reflecting drought-sensitivity, yellowpoplar trees reduced incremental growth
during the drought years 1999 and 2002
(Fig. 6). Oak species (not pictured), in
contrast, did not significantly vary in
incremental growth.
•GPS coordinates.
2. Tree data (223 yellow-poplar trees / 485 total trees):
•species;
•diameter (DBH);
•number of 12’ log lengths exceeding FAS/1F grade;
Significant relationships: Variations in
crown light, crown position, and
crown density were significantly
associated with changes in incremental
growth.
•FHM crown conditions and damages.
•Increment cores (150 trees)
3. Ordinal Tree Condition Data
Yellow-poplar trees were rated (good, fair, or poor condition), based on the
severity observed in several decline symptoms. This multi-factor approach is
similar to one developed by the authors when studying ash decline, and
overcomes limitations of using single FHM parameters for describing yellowpoplar decline.
Figure 6: Radial Growth in Yellow-poplar in 12 SE Indiana Woods
with Yellow-poplar Decline
Drought: Yellow-poplar decline is strongly associated with prolonged
drought events. Decline symptoms were most pronounced on exposed
slopes, and first appeared after the 1999 and 2002 drought.
Suppressed trees: Decline symptoms and mortality were most
pronounced on smaller-diameter trees with suppressed crowns.
Commercial thinning / salvage operations do not appear warranted or
feasible when single-year drought events occur, because trees most
affected are of low economic value.
Use of FHM/FIA dataset: Several FHM crown condition parameters
were strongly correlated with yellow-poplar decline. Insufficient Indiana
P3 crown condition data, however, restricts use of the current on-plot
data set to extrapolate the extent of yellow-poplar decline statewide.
Figure 5: Relationship of Crown Density and Tree
Condition Chi-Square = 16.41699, df = 9, p = .0587
•slope;
•aspect;
Discussion
No correlations: Incremental growth
changes were not significantly correlated
with decline, live crown ratio, DBH,
foliage transparency or dieback.
Mortality: Plotting of FIA mortality data (1985-2005) closely follows
both the distribution of drought-vulnerable soils and areas of the state
with reported decline, further indicating yellow-poplar decline to be
drought-associated.
Dan Johnson – Indiana University